Explosively separable fastener



Jan. 28, 1964 c. K. BROWN EXPLOSIVELY SEPARABLE FASTENER Filed Aug. 4. 1960 INVEN TOR. CLARENCE K. BROWN BY wwm A GENT United States Patent antenna. EXPLQSHVELY SEPARABLE FASTENER Clarence K. Brown, Bellilower, Calif assignor to lili- Shear Corporation, Torrance, Calif., a corporation of California Filed Aug. 4, 19st Ser. No. 47,415 1 (Tlaim. (Cl. 85-1l) This invention relates to a fastener which may be explosively separated.

An object of this invention is to provide a fastener that will join structural members, primarily in shear applications, with the full shear strength for the size of the fastener and with the capability of withstanding the tensfle loads present in such a joint and the necessary installation torques; yet this fastener to be capable of being separated by a relatively small charge of solid propellant material which may be detonated from a remote point by an electrical signal.

A further object of this invention is to provide an explosive bolt which may be installed in an unarmed condition and which may be armed or disarmed for safety at any tirne.

Conventional explosive bolts have been made in the past but have always containedan explosive charge buried in a recess within the shank. The structure of the bolt had tobe weakened to provide :for fracture due to the explosive detonation; however, the bolt structure could not be weakened beyond a point Where the useful strength of the bolt would be excessively impaired so a relatively large explosive charge was required to separate the bolt. This excessive explosive energy could do damage to adjacent structures. Moreover, this type of bolt would have to be installed in an armed condition without the capability of being disarmed.

According to this invention a separable bolt is made in two primary sections, one having a threaded end and the other a head end. The threaded end section has a re duced diameter which fits a longitudinal bore in the headed end. A third member is employed to retain the reduced diameter of the threaded section of the bolt with in the headed section. The longitudinal bore of the headed end is adapted at the head to receive a conventional explosive squib, the retaining member is of a size and form which will fail in shear upon detonation of the squib.

According to a preferred but optional feature of the invention sealing means may be provided between the threaded section of the head section of the bolt to confine the explosive detonation of the squib and direct its full energy to separating the bolt.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, of which:

FIG. 1 is a side elevation partially in cross-section of one embodiment of this invention shown assembled in structure with a squib and nut in place;

FIG. 2 is a cross-section of the device of FIG. 1 taken at line 22 of FIG. 1;

FIG. 3 is a cross-section taken at line 3-3 of FIG. 1;

FIG. 4 is a side elevation in cross-section of another embodiment of the invention;

FIG. 5 is a cross-section taken at line 5-5 of FIG. 4.

In FIG. 1 there is shown a preferred embodiment of this invention. The fastener is shown with two primary sections, 33 being a threaded member and a head member 16. The threaded member 33 is cylindrical in shape with a thread 32,, a shank portion 31, and a reduced cylindrical diameter 30. The head end 23 is of geometric shape to accept a Wrench and has a cylindrical shank portion 34. The bore 26 is shown coaxially through head "tee Li member 16 and is of a size to receive a reduced shank diameter 30 of thread end 33 at the shank end of head member 16. At the head end 23 of head member 16 the bore 26 has a thread 17 to accept a standard squib 18. Such a squib conventionally has an explosive chamber 24 and electrical leads l9 and 22 which may be attached to a source of D.C. current 2% and which squib will be detonated by closing a switch 21. In manufacturing this fastener threaded end 33 is inserted into bore 26 of head member 1d and a transverse hole is drilled through both members to accept a shear pin 29. The fastener in FIG. 1 is shown fastening two sheets of structure 14 and 15*, shown in phantom, held by nut 12, also shown in phantom.

As a preferred but optional feature the reduced diameter 3d of thread end 33 may have an undercut 27 of a size to receive an elastomeric O-ring sealing member 28. This sealing member prevents leakage of gaseous products of the explosive charge contained in the squib upon detonation and concentrates the entire force of the explosion on surface 25 of thread end 33 to effect shear failure of pin 29, thus separating the fastener and the joint.

in FIG. 4 there is shown another embodiment of th's invention. There are two primary members again, a threaded member 5t) and a head member 4b. Threaded end Si? is cylindrical in shape with a thread 49 at one end, a cylindrical shank S1 and a reduced cylindrical diameter 4/7 adjacent to shank 51. The reduced diameter 47 term'mates in a tapered surface 4 In the reduced diameter 47 there is an undercut of rectangular section 36. Head member it has a smooth cylindrical shank 46 which is preferably the same diameter as the shank 51 of thread member 5t. There is an enlarged head 48 of geometrical shape to accept a wrench. A longitudinal coaxial bore 42, extends through head member 4%, and at the end remote from the head, is enlarged to the same diameter as the reduced shank 4'7 of the threaded member 5d and terminates in a tapered face 641 to permit the reduced diameter 47 of threaded member 5%} to be completely inserted into the bore of member 46. In the tapered face 64- of this enlarged bore there is a recess 38 which is of a shape and size to accept an elastomeric sealing member 39. The bore reduces in size to produce a passage 52 which extends through the head of head member 49. The bore d2 terminates in a threaded area 41 which is adapted to accept a conventional explosive squib. Reraining member 37 is a split, resilient ring which engages groove as in threaded member 5% and groove 53 in head member 46* to retain both parts in assembly. To assemble the device sealing ring 39 must first be inserted into recess 38. The retaining ring 37 must be compressed and inserted into groove 53. Groove 53 should be of sufficient depth to allow expansion of ring 37 as the tapered nose 44 of threaded member 5%) is pushed into bore 45 of head member it), thereby expanding retainer 3'7 until it snaps into groove 36 of the threaded member 5%. After assembly of threaded end to head end 4d a hole 56 may be drilled at the parting line 54 at the shank diameter of the two mating parts and transverse to the center line of the two parts and a pin 55 inserted to prevent relative rotation of threaded end 50 with head end it) during installation torquing of a nut. A conventional squib 58, with electrical leads 59 and at is shown in place in the head end 48 of the stud. This squib may be removed at any time to disarm the stud without affecting the structural integrity of the stud or the structure that is assembled with the stud.

In use the fastener of FIG. 4 would be inserted into structure which comprises two or more sheets or members and installed with a conventional nut. A conventional type of explosive squib 58 would be installed in the head end of the fastener with an explosive charge thereby contained within cavity 52. External electrical leads 59 and 60 would connect to a source of power and upon completing, the circuit the explosive would detonate. Confined in close quarters the resultant shock Wave would act upon surface 43 of threaded member '50 and react against the body of the squib to cause retaining member 37 to fail in shear, blowing both parts out of the struc ture longitudinally and thereby separating the structure. Due to this design, the retaining member may be made of a strength that will require a very minimum of explosive to create a reliable separation.

This invention is not to be limited by the embodiments shown in the drawings and described in the description, but only in accordance with the scope of the appended claim.

I claim:

A threaded stud assembly for explosive separation which comprises a first threaded member, said member having a threaded end, a smooth shank portion adjacent the threaded end, a reduced coaxial cylindrical section adjacent said smooth shank portion, said reduced cylindrical section terminating in a tapered face at the end opposite said threaded end, said tapered face truncated to form a fiat end to said first threaded member, an external annular groove in said reduced cylindrical section adjacent said tapered face; a second member, said second member having a head end, said head end of geometric shape adapted for wrenching, said second member having a. coaxial bore extending through said second member, said bore at the end opposite the head end adapted to accept said reduced cylindrical section of said first member in close engagement, said enlarged bore terminating in a tapered shoulder, said tapered shoulder adapted to fit closely with said tapered face of said reduced cylindrical section of said first member, an internal annular groove adjacent said tapered shoulder, said internal groove adapted to register with said. external groove of said first threaded member when said first and second members are assembled one to the other, said bore adapted at said head end of said second member to receive an explosive squib to form a closed chamber for maximum explosive effect in combination with said fiat end of said tapered face of said reduced cylindrical section and said coaxial bore of said second member; a retaining ring, said ring split at one side, said ring adapted to engage said external annular groove of said first threaded member and said internal annular groove of said second member to retain said members in assembly; key means between said first threaded member and said second member to prevent relative rotation; sealing means between said tapered face of said reduced cylindrical section of said first member and said tapered shoulder of said bore of said second member adapted to confine an explosive force Within said bore for maximum explosive effect.

References Cited in the file of this patent UNITED STATES PATENTS 1,390,645 Ritter Sept. 13, 1921 2,061,835 Haines Nov. 24, 1936 2,165,656 Ryan July 11, 1939 2,492,006 Raybould Dec. 20, 1949 2,577,009 Frantz Dec. 4, 1951 2,653,504 Smith Sept. 29, 1953 2,809,584 Smith Oct. 15, 1957 2,938,429 Jaglowski et a1. May 31, 1960 3,032,356 Botsford May 1, 1962 

